1. Field of the Invention
The present invention relates to an exhaust gas purifying catalyst which purifies exhaust gas discharged from automobile engines and relates to a method of manufacturing the exhaust gas purifying catalyst.
2. Description of the Related Art
An exhaust gas purifying catalyst converts hazardous gas contained in exhaust gas, such as hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxides (NOx), into nonhazardous water and gas with catalysis of noble metal, such as platinum (Pt), palladium (Pd), and rhodium (Rh). A widely-known exhaust gas purifying catalyst has a structure in which a substrate has a honeycomb structure with a number of through-holes formed and a catalyst layer is formed on a wall of each through-hole. In this catalyst layer, noble metal such as Pt, Pd, and Rh is supported by a carrier made of oxide.
As a conventional exhaust gas purifying catalyst, the following catalyst (see Japanese Patent Unexamined Publication No. 2001-104783) is disclosed. A first layer composed of inorganic oxide is formed on the substrate, and a second layer composed of an inorganic fiber material to catch granular materials contained in exhaust gas is formed on the first layer. A catalytic component thereof is supported at least in the first layer. In the second layer of this exhaust gas purifying catalyst, the inorganic fiber material has a mesh structure in order to catch the granular materials such as soot contained in exhaust gas of diesel engines.